The present invention relates to a flexible conduit, such as one used or made for obtaining a sterilizable hose for medical or surgical use, for example for conveying a gas to a patient, it being understood that such a conduit may have many other applications.
In accordance with document U.S. Pat. No. 4,343,672, a process is described for obtaining a flexible conduit, said conduit comprising a profiled strip, having, as one piece, a web with two mutually complementary marginal edges and at least one rib projecting on one side from the web, according to which process the profiled strip is obtained by extruding a crosslinkable plastic, the profiled strip, after it has been obtained by extrusion, is wound about an axis in a helix with touching turns, so that the complementary marginal edges of the profiled strip, belonging respectively to two different turns, form between them, directly, a sealed joint, and the wound profiled strip, with directly touching turns, is crosslinked in order to obtain a one-piece flexible conduit.
In practice, and in particular with regard to a hose for medical or surgical use, a flexible conduit of the type defined above must be joined, at least at one end, to an end-piece, which in general is handled, and in particular is repeatedly fitted onto and removed from a complementary fixed part. This end-piece is generally a piece which is sealably attached and fitted onto the said end of the conduit.
Such an end-piece is the cause of many drawbacks.
That region of the flexible conduit which is adjacent to the end-piece is subjected to repeated bending because of the manipulation of the hose or of the end-piece and necessarily constitutes a region of weakness. This is particularly true in the case of a hose for medical or surgical use, which is continually being connected to and disconnected from a fixed part, or fitting, of another hose or of an apparatus, for example a respirator. Furthermore, and in this application, the repeated sterilization of the hose also helps to weaken the region adjacent to the end-piece. In this medical and surgical use, a weak region of this kind is unacceptable since it contravenes the safety requirements of the medical hose, in terms of sealing with respect to the inside or the outside of the conduit.
This end-piece also complicates the manufacture of the final hose, by requiring the manufacture of an independent piece, this piece then having to be sealably fitted onto the flexible conduit. In certain cases, the difference in inside diameter between the flexible conduit itself and the end-piece additionally requires the end-piece to be adapted to this variation in inside diameter or requires an additional adapting piece to be provided and fitted onto the flexible conduit.
The object of the present invention is to remedy these drawbacks.
More particularly, the subject of the invention is a process for obtaining a flexible conduit of the type defined above, making it possible to obtain, in a monolithic manner, a single piece incorporating not only an impermeable internal tube and a helical external structure supporting the internal tube, but also the end-piece or end-pieces required for the use of the flexible conduit.
For this purpose, the invention provides a process for obtaining a flexible conduit comprising a profiled strip having, as one piece, a web with two mutually complementary marginal edges, and at least one rib projecting on one side from the web, the process comprising:
(a) winding the profiled strip, after it has been obtained by extrusion, about an axis in a helix with touching turns so that the complementary marginal edges of the profiled strip, belonging respectively to two different turns, form between them, directly, a sealed joint; and
(b) crosslinking the wound profiled strip, with directly touching turns, to obtain a one-piece flexible conduit, wherein during the winding of the profiled strip, the winding pitch of the profiled strip is varied in order to control or modulate the supply of deformable plastic manner along the length of the conduit.
The expression xe2x80x9cdirectly touching turnsxe2x80x9d should be understood to mean the formation of a sealed joint at each marginal edge of the profiled strip, this joint connecting, in a sealed manner, without the interposition of an adhesive, the each marginal edge to the adjacent marginal edge of an adjacent turn. This joint is obtained directly by bonding between the two adjacent marginal edges, along the entire appropriate grouting outline, for example with straight, obliquely chamfered or xe2x80x9csteppedxe2x80x9d edges.
Next, by virtue of the above defined process, it is possible, during step (a), to vary the winding pitch of the profiled strip along the length of the conduit, thereby making it possible to control or modulate along the length of the conduit the supply of malleable or deformable plastic and the amount of material available per unit length.
Preferably, the winding pitch is decreased during step (a), for example at one end of the conduit, in order to locally increase the thickness of plastic available in the malleable or formable state, before crosslinking.
If the thickness of deformable plastic is increased in this way during step (a) at one or both ends of the conduit, it is thus possible, while the plastic is still malleable, to form an end-piece in this thickness. This plastic is then crosslinked in order to obtain a flexible conduit in which the end-piece or the two end-pieces are made as one piece with the impermeable internal tube and the external surface of the flexible conduit interrupts or extends the helical external structure.
Preferably, according to step (a), the profiled strip is wound, as it leaves the extrusion die, around a bar which is moved in translation and in rotation, the external cross section of which sets or predetermines, in negative, the internal cross section of the flexible conduit, while the plastic is still deformable or malleable.
This operating choice is particularly advantageous in that it allows the internal cross section to be varied or modified, along the length of the latter, for example in order to change the internal diameter of the conduit from a nominal value to another value, which is lower or higher, determined by an end-piece or fitting, without any other complementary piece or component, such as an adapter.